Printing method and system for converting color tones to lighter and darker values for printing with light and dark inks

1. A printing method comprising: using a print control apparatus for converting a tone value indicating a tone of a certain color to a first light tone value indicating a tone of a light color using a predetermined number of tones, and a first dark tone value indicating a tone of a dark color using a predetermined number of tones; converting the first light tone value to a second light tone value indicating a tone of the light color with a smaller number of tones than the predetermined number of tones, based on a table for the light color; converting the first dark tone value to a second tone value indicating a tone of the dark color with a smaller number of tones than the predetermined number of tones, based on a table for the dark color other than the table for the light color; ejecting a light ink based on the second light tone value to form a light dot in the light ink on a medium; ejecting a dark ink based on the second dark tone value to form a dark dot in the dark ink on the medium; and expressing a tone of the certain color on the medium with the light dot and the dark dot.

2. A printing method according to claim 1 , wherein the table for the light color and the table for the dark color are set such that a maximum number of the light dots per unit area is different from a maximum number of the dark dots per unit area.

3. A printing method according to claim 2 , wherein the light dot can be formed in a plurality of sizes depending on the second light tone value, and the dark dot can be formed in a plurality of sizes depending on the second dark tone value.

4. A printing method according to claim 3 , wherein the table for the light color and the table for the dark color are set such that a maximum number of the light dots in the smallest size per unit area is larger than a maximum number of the dark dots in the smallest size per unit area.

5. A printing method according to claim 1 , wherein the table for the light color and a dither matrix are used in converting the first light tone value to the second light tone value, and the table for the dark color and the dither matrix are used in converting the first dark tone value to the second dark tone value.

6. A printing system comprising: a print control apparatus that converts a tone value indicating a tone of a certain color to a first light tone value indicating a tone of a light color using a predetermined number of tones, and a first dark tone value indicating a tone of a dark color using a predetermined number of tones, that converts the first light tone value to a second light tone value indicating a tone of the light color with a smaller number of tones than the predetermined number of tones, based on a table for the light color, and that converts the first dark tone value to a second tone value indicating a tone of the dark color with a smaller number of tones than the predetermined number of tones, based on a table for the dark color other than the table for the light color; and a printing apparatus that ejects a light ink based on the second light tone value to form a light dot in the light ink on a medium, that ejects a dark ink based on the second dark tone value to form a dark dot in the dark ink on the medium, and that expresses a tone of the certain color on the medium with the light dot and the dark dot.